An electrophotographic image forming apparatuses can include, for example, an LED head having a plurality of LEDs (light emitting elements) arranged in a row, and forms an electrostatic latent image by exposing a photoreceptor line by line with this LED head. A color image forming apparatus includes a plurality of above-mentioned LED heads corresponding to each color, and forms an electrostatic latent image with each LED head, so that a color image is ultimately formed on a body to be transferred, with each color image developed from respective electrostatic latent images overlapped one after another.
Here, it is ideal that an LED head includes LEDs all aligned in a straight line. However, such an ideal LED head is difficult to manufacture, and thus, in an actual LED head, one or more of the LEDs can be distributed out of a straight line. Moreover, this distribution tendency of LEDs is different for each LED head. Consequently, the above image forming apparatus may have a different shape of exposing line for each LED head corresponding to each color, and, as a result, a color image having a position deviation (color deviation) between each color image is formed on a body to be transferred, thereby causing deterioration of image quality.
In response, an image forming apparatus that conducts correction processing for restraining deterioration of image quality caused by the difference of distribution tendency of LEDs has been proposed. In particular, when an LED head of each color forms an exposing line, a light emission timing of an LED head corresponding to one color is corrected so that an position deviation relative to the other color image as a reference color image is offset.